The present invention broadly relates to an automatic detection device for positively sensing the ejection or discharge of a workpiece from a cyclically operating, machine, such as a press, for example. Presses and similar machinery of the type adapted to successively perform a work operation on workpieces are frequently operated by means of an automatic control circuit to achieve automatic cyclical operations. Such machinery further includes automatic ejection devices for extracting and discharging a workpiece after each operating cycle and may also advantageously be equipped with automatic loaders for feeding new workpieces into the machine at the completion of each operating cycle.
It has heretofore been proposed to include in such automatic machinery detection devices for sensing a malfunction in one or more operating steps of the machine cycle to abruptly stop machine operation in the event of a malfunction thus avoiding damage to the machine components and/or workpieces being processed. In automatic presses, for example, it has heretofore been proposed to employ detection devices for detecting the ejection of a workpiece from the press at the completion of an operating cycle so as to avoid a so-called double strike. Such prior art devices frequently employ various photoelectric cell arrangements, probes, and other sensing devices for detecting the discharge of a part from the press. Typical of such detection devices is the deflectable probe disposed in a discharge chute in accordance with the arrangement illustrated in U.S. Pat. No. 3,656,139. Unfortunately, detection devices of the types heretofore known have been susceptible to being triggered by pieces of flash metal, the machine operators hands, and extraneous matter in the vicinity of the machine producing a false indication that workpiece ejection has occurred whereby a double strike occasionally occurs causing severe damage to the press dies.
The present invention overcomes the problems and disadvantages associated with prior art devices for ejected workpieces which is less susceptible to inadvertent triggering providing positive indication that actual ejection had occurred. The detection device of the present invention is further characterized as being of simple design, durable operation and control, versatile use, and economical manufacture.